Installation switching devices may, for example, be circuit breakers, residual current devices, motor protection switches or selective main line circuit breakers.
By way of example, one circuit breaker of this type is disclosed in DE 10 2008 006 863 A1. In a circuit breaker such as this, a short-circuit current is disconnected with the aid of an impact-type armature. The field of a magnet coil, through which the current flows, excites the magnetic circuit within the electromagnetic short-circuit current release, and the impact-type armature is thus moved by electrodynamic interaction. The impact-type armature is coupled to a striking pin which strikes the contact lever such that the contact point is opened, and which at the same time acts on the switching mechanism, leading to unlatching of the switching mechanism and therefore to the contact point being kept permanently open, until the switching mechanism is latched again, only after which can the contact point be closed again.
In known installation switching devices, overcurrent tripping takes place with the aid of a thermomechanical tripping element, generally a thermal bimetallic strip. The overcurrent causes heating of the thermal bimetallic strip, resulting in the strip bending. In the bent state, the thermal bimetallic strip unlatches the switching mechanism by an appropriate link by means of a switching mechanism operating element, in response to which the contact point is likewise permanently opened until the switching mechanism is latched again, only after which can the contact point be closed again.
The switching mechanism disclosed in DE 10 2008 006 863 A1 has a latching point which is formed between a tripping lever and a latching lever. In addition, an intermediate lever is provided, which interacts with a contact lever. Furthermore, a switching handle is provided, which is coupled via a bracket to the intermediate lever, with the intermediate lever being mounted such that it can move relative to the latching lever. When the latching point is latched, a rigid lever chain is formed from the switching handle via the bracket and the intermediate lever to the contact lever. When the latching point is unlatched, the rigid coupling collapses and the intermediate lever can be moved relative to the latching lever. The latching point can be unlatched by acting on the tripping lever in order to pivot it such that the latching point is unlatched. For this purpose, DE 10 2008 006 863 A1 provides a striking lever, which acts on the tripping lever when it pivots, and pivots the tripping lever in order to unlatch the latching point. The impact-type armature of the magnetic short-circuit current release and the thermal bimetallic strip of the overcurrent release both act on the striking lever, and the tripping lever is moved indirectly via the striking lever to its unlatched position.
In known installation switching devices, the response rate of the magnetic release is limited, since it includes a plurality of mechanical subsystems, each of which has a certain amount of mechanical inertia. The current limiting in the event of a short circuit is therefore also limited. Furthermore, in known installation switching devices, temperature compensation is required for the overcurrent release.
For fitting, known circuit breakers are normally mounted on a top-hat rail by means of a quick-release attachment. For electrical protection of telecommunications facilities, a circuit breaker for DC applications is often used, with very fast short-circuit disconnection and overcurrent tripping independently of the temperature. When used in switchgear cabinets, for example for telecommunications infrastructure, 19-inch rack inserts with a specific height are often used. This height has a subdivision unit of 1 U, approximately 44.45 mm. Switching devices for use in these switchgear cabinets should not exceed a height of 1 U. In addition, the switching device should make direct contact with and be mounted on a copper rail. The normal physical size of known circuit breakers therefore cannot be used.